Method and system for forming a recess in a tubular workpiece

ABSTRACT

A roller support block  10  supports rolling rollers ( 6˜9 ) in four stages and moves in a guide hole ( 13 ) of a pipe holder ( 5 ) to sequentially bring the rolling roller into pressure contact with a pipe ( 2 ) held immovable by the pipe holder ( 5 ) through an aperture ( 35 ) made in the pipe holder ( 5 ). In this process, the first-stage rolling roller ( 6 ) first comes into rolling pressure contact with the pipe for preliminary shaping of a recess. Subsequently, the second-stage and third-stage rolling rollers ( 7, 8 ) advance the preliminary shaping to enlarge and deepen the recess. Finally, the fourth-stage rolling roller  9  finally shapes the recess to a first locking groove ( 3  or  4 ).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International PatentApplication No. PCT/JP2004/015542, filed Oct. 14, 2004 (incorporatedherein by reference), which in turn claims priority from Japanese PatentApplication No. JP2003˜353242, filed Oct. 14, 2003.

FIELD OF THE INVENTION

The present invention relates to a method and a system for forming arecess in a tubular workpiece like a pipe.

BACKGROUND OF THE INVENTION

Modern compartment seats of vehicles are equipped with headrests toprotect passengers' heads upon collision. Headrests are typicallyattached to seat backs via stays, and users can adjust them in height bypulling them up or pushing them down. A typical mechanism for adjustmentof the headrest's height includes hooks anchored in a seat back, and aseries of locking grooves formed along each headrest stay.

In the history of headrests, their stays were first made of solid rodsthat are round in cross section, and solid rods were substituted bypipes (hollow cylinders). Further, along with recent movements towardlightweight vehicles, the use of thin-wall pipes is desirable.

In case of solid rods and thick-wall pipes, locking grooves can beformed by locally cutting their walls with a cutter on a millingmachine. However, grooves in thin-wall pipes, having walls thinner thanthe required depth of locking grooves, cannot be formed by cutting.Therefore, a different method is required to form grooves that indentfrom outer circumferential surfaces of thin-wall pipes to define sharpengagement surfaces having angled edges at their outer ends to maintainreliable engagement with hooks.

Japanese Patent Laid-open Publication No. JP-H08-90126 proposes a methodof forming locking grooves of a headrest stay of a support rod of ahandbrake by inserting a core member inside a pipe and depressing theouter circumferential surface of the pipe with a punch.

Japanese Patent Laid-open Publication No. JP-2000-197922 proposes amethod of forming a recess in a hollow shift fork shaft of a manualtransmission for receiving a check ball by suing a press machine underthe presence of a core member inserted into the hollow shaft. Thispublication also proposes a method of removing the core member from theshaft after forming the recess by rotating the core member having aunique configuration.

Japanese Patent Laid-open Publication No. JP-2002-137673 is directed toa method of forming locking grooves at opposed positions of two longerparallel segments of a headrest stay made of a channel-shaped pipehaving the two longer segments connected by one shorter segment. Thispublication proposes to form locking grooves by thrusting the pipebetween a pair of roll punches located face to face under the presenceof support rolls set aside the roll punches to support them.

Japanese Patent Laid-open Publication No. JP-2002-210519 proposes amethod of forming locking grooves of a headrest stay through twomanufacturing steps, i.e. a preliminary shaping step and a final shapingstep. In the preliminary step, this method forms a recess indenting fromthe circumferential surface of a pipe by driving a rotating punch downonto the exposed circumferential surface of the pipe while supportingthe pipe in an arcuate groove of a holder. In the next final shapingstep, this method forms the locking groove by moving a press punch alonga guide groove while covering the full circumference of the pipe with aholder cover having the guide groove extending along the recess.

Japanese Patent Laid-open Publication No. JP-2003-9991 proposes a methodof forming locking grooves of a headrest stay by thrusting a punchhaving an end surface of a unique configuration onto a pipe.

Japanese Patent Laid-open Publication No. JP-2003-71522 proposes amethod of forming locking grooves of a headrest stay by thrusting apress tool having a unique configuration onto the circumferentialsurface of a pipe while driving the tool transversally of the lengthwisedirection of the pipe under the presence of a core member inserted inthe pipe.

To form a recess required to define such a sharp engagement surface at aportion of the outer circumferential surface of a pipe, just like alocking groove of a headrest stay, it is important to prevent bluntnessof the edge of an engagement surface in the recess as theabove-introduced publications point out as well.

In addition, complicated tasks or steps for forming such recesses in apipe invite an increase of the cost. Therefore, to reduce or minimizethe cost, it is advantageous that recesses of a desired configurationcan be formed in a pipe in a single manufacturing step.

SUMMARY OF THE INVENTION

Under the circumstances, there is a need for a method and a systemcapable of forming a recess of desired configuration in a tubularworkpiece like a pipe in a single continuous step.

It is also desirable that such a recess can be formed in a tubularworkpiece without inserting a core member inside the workpiece.

There is a further need for a method and a system capable of formingsuch a recess in a tubular workpiece having a thin wall like a thin-wallpipe.

It is also desirable that such a recess can be formed in a tubularworkpiece having a thin wall and a high tensile force such as athin-wall, highly tensile pipe.

It is also desirable that a recess having a sharp engagement surfacehaving an angled edge, such as a locking groove, can be formed on atubular workpiece having a thin wall such as a thin-wall pipe in asingle step.

It is also desirable that such a recess can be formed in a straighttubular workpiece like a straight pipe before it is bent to achannel-shaped member, for example, such as a headrest stay.

According to an embodiment of the invention, there is provided a methodof forming a recess in a tubular workpiece comprising:

-   -   preparing a set of rolling rollers in multiple stages capable of        sequentially interfering the workpiece in an intersecting        direction;    -   having the rolling rollers sequentially get into pressure        contact with the workpiece by relative movement between the        rolling rollers and the workpiece to bring about preliminary        shaping and final shaping and thereby form the recess in the        workpiece; and    -   preparing a workpiece holder capable of holding the workpiece        immovable by enveloping the workpiece and having an aperture        through which the rolling rollers can sequentially interfere        with the workpiece, wherein the rolling rollers get into        pressure contact with the workpiece through the aperture.

In this method, a workpiece holder having an aperture is preferably usedto support the workpiece and expose a portion of the workpiece to beprocessed for forming the recess. To ensure that the recess defines asharp engagement surface having an angled edge, at least a portion ofthe contour of the aperture adjacent to the engagement surface of therecess in the workpiece preferably makes substantially no gap from thecontour of the final-stage rolling roller.

According to another embodiment of the invention, there is provided asystem for forming a recess in a tubular workpiece comprising:

-   -   a roller support block that holds a set of rolling rollers in        multiple stages aligned in a row and permits the individual        rolling rollers to rotate; and    -   a workpiece holder having a workpiece-receiving hole        substantially equal in cross-sectional configuration to the        workpiece and capable of holding the workpiece immovably in the        workpiece-receiving hole, said workpiece holder having an        aperture exposing a part of the workpiece held in the        workpiece-receiving hole,    -   wherein the rolling rollers sequentially come into pressure        contact with the workpiece through the aperture along with        relative movement between the roller-receiving block and the        workpiece holder, and thereby performing preliminary shaping and        final shaping sequentially to form a recess in the workpiece.

The workpiece holder may be divided in the moving direction of theroller support block. In case the roll support block moves vertically,the workpiece holder is divided to upper and lower portions, and one ofthe divisional portions may be moved to grip or release the workpieceinserted between them.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining the basic concept of the presentinvention;

FIG. 2 is a cross-sectional view of a locking groove formed to indentfrom the outer surface of a pipe typically used as a headrest stay;

FIG. 3 is a cross-sectional view of another locking groove formed toindent from the outer surface of a pipe typically used as a headreststay;

FIG. 4 is a cross-sectional view taken along the IV-IV line of FIG. 3:

FIG. 5 is a diagram for explaining the outer circumferentialconfiguration of rolling rollers used to form the locking groove shownin FIG. 3;

FIG. 6 is a diagram for explaining a modification in positions of therolling rollers;

FIG. 7 is a perspective view of a pipe holder that is a component of atest system;

FIG. 8 is a perspective view of a roller support block that is acomponent of the test system;

FIG. 9 is a diagram showing how the rolling rollers locally depress apipe;

FIG. 10 is a diagram showing the contour of an aperture through whichthe rolling rollers can locally depress the pipe;

FIG. 11 is a schematic plan view of a common roller support blockpreferably employed in a mass production type system;

FIG. 12 is a schematic front elevation of the common roller supportblock preferably employed in the mass production type system;

FIG. 13 is a schematic diagram of a modified system having rollingrollers held stationary to form recesses in moving pipes;

FIG. 14 is a diagram for explaining the outline of a mass productiontype system remodeled from a press; and

FIG. 15 is an upper diagonal view of a guide member having a guide holeand a pipe holder, which are located side by side.

DETAILED DESCRIPTION OF THE INVENTION

Some embodiments and specific examples of the present invention will nowbe explained in detail with reference to the drawings.

FIG. 1 shows the basic concept of the invention for forming a recess ina tubular workpiece typically of a metal. The recess-forming systemshown in FIG. 1 is used to form locking grooves of a headrest stay.

The headrest stay, as a final product, is a channel-shaped or M-shapedmember made by bending a straight pipe to two longer pipe segments andone shorter pipe portion connecting the longer pipe segment, as alreadyknown in the art. The longer pipe segments have a plurality of lockinggrooves formed in intervals in their axial directions. The illustratedheadrest stay has a first locking groove 3 (approximately 1.5 mm deep)having a channel-shaped cross section as shown in FIG. 2, and a secondlocking groove 4 (approximately 1.5 mm deep) defined by a vertical planeand an opposed tapered plane as shown in FIGS. 3 and 4. Therecess-forming system 1 can be used to form these first and secondlocking grooves 3, 4.

The recess-forming system 1 can be used to form locking grooves in apipe bent to the shape of a headrest stay from a straight pipe asexisting techniques do. Moreover, the recess-forming system 1 can formlocking grooves in a straight pipe before being bent to the form of aheadrest stay. That is, locking grooves 3, 4 can be formed in a straightpipe of a predetermined length by the recess-forming system 1, and thestraight pipe may be bent later to manufacture a channel-shaped orM-shaped headrest stay.

To manufacture various types of headrest stays, it is advantageous toform a desired number of locking grooves 3, 4 in metal pipes bent to theforms of final products, including channel-shaped and M-shaped ones.Actually, there are many types of headrest stays. For example, some havelocking grooves only in opposed surfaces of longer pipe segments opposedto each other. Some have them in the opposed planes and the planesbehind the opposed planes. Some have them on one or both of front andrear planes. Therefore, if the locking grooves 3, 4 are formed after thepipes are bent to the shapes of the final products, it is necessary toprepare different forming dies for respective types of headrest stays.However, if the locking grooves 3, 4 can be formed before the pipes arebent to the shapes of the final products, the straight pipes, alreadyhaving locking grooves, can be bent later so as to bring the grooves 3,4 at locations required for the individual types of headrest stays.Thus, various types of headrest stays can be manufactured.

The recess-forming system 1 includes a pipe holder 5 for holding a pipestationary, and a roller support block 10 that supports a plurality ofrolling rollers (rolling dies for form rolling) 6˜9. The pipe holder 5includes a fixing block 11 and a main holder block 12 that can tightlyhold a pipe between them to prevent the pipe 2 from displacement in itslengthwise direction and rotation about the axial line. The pipe holder5 has a guide hole 13 formed to extend in the vertical direction at aposition adjacent the pipe 2.

The rolling rollers 6˜9 are supported by the roller support block 10 toalign in intervals along the axial line of the guide hole 13, andsupported for free rotation on the roller support block 10 by individualshafts 15˜18. The roller support block 10 is inserted into the guidehole 13 from above to work out a desired recess, i.e. the locking groove3 or 4, in the pipe 2 during a single reciprocal movement, preferablyfirst down and next up, in the guide hole 13.

For easier explanation, the rolling rollers are individually named thefirst-stage rolling roller 6, second-stage rolling roller 7, third-stagerolling roller 8, and fourth-stage rolling roller 9 from the one firstentering into the guide hole 13 to the one finally entering same asshown in FIG. 1. Further, the first-stage rolling rollers to thefourth-stage (final-stage) rolling rollers 6˜9 are often called thefirst rolling rollers to the fourth-stage (final-stage) rolling rollers6˜9 hereafter. The support shafts 15˜18 of the first to fourth rollingrollers 6˜9 lie on a common vertical line L parallel to the direction ofrelative movement between the rolling rollers 6˜9 and the pipe 2, anddiameters D of the first to fourth rolling rollers 6˜9 graduallyincrease from the first rolling roller 6.

In greater detail, diameter D1 of the first rolling roller 6 nearest tothe guide hole 13, that is, nearest to the pipe 2 in position, issmaller than the diameter D2 of the second rolling roller 7 upwardlynext to the first rolling roller 6. The diameter D2 of the secondrolling roller 7 is smaller than the diameter D3 of the third rollingroller 8. The diameter D3 of the third rolling roller 8 is smaller thanthe diameter D4 of the fourth rolling roller 9. Here is the relation ofD1<D2<D3<D4.

Outer circumferential surfaces of the first to fourth rolling rollers6˜9 have outer circumferential surfaces (hereinafter often calledshaping surfaces as well) corresponding to the shape of the firstlocking groove 3 (FIG. 2) or the second locking groove 4 (FIGS. 3 and4). FIG. 5 shows the shaping surface of the fourth rolling roller 9(solid line) together with shaping surfaces of the first to thirdrolling rollers 6˜8 (broken lines). It will be readily understood fromFIG. 5 that a groove (second groove 4 of FIG. 3 in the illustratedexample) first depressed shallow by the first rolling roller 6 isgradually increased in width and depth by the second and third rollingrollers 7, 8 until reaching to the width and depth finally made by thefourth rolling roller 9. That is, the fourth rolling roller 9, which isthe final-stage rolling roller, finishes the final configuration of thefirst locking groove (FIG. 2) or the second locking groove 4 (FIGS. 3and 4) of the pipe 2.

More specifically, when the roller support block 10 moves under theguide by the guide hole 13 of the pipe holder 5, the first rollingroller 6 first rolls on the pipe 2 while keeping tight contact therewithand locally depresses the outer circumferential surface of the pipe 2 inform of a recess. Subsequently, the second and third rolling rollers 7,8 gradually getting larger in diameter sequentially roll on the pipe 2to enlarge and deepen the recess. That is, the amount of depression forthe recess made by sequential compression from the rolling rollersincreases gradually. After that, the fourth rolling roller 9 as thefinal-stage rolling roller rolls on the pipe 2, and further enlarge anddeepen the recess, and here is completed the final configuration of thefirst locking groove 3 or the second locking groove 4.

The shaping surfaces of the first to third rolling roller 6˜8 used forpreliminary shaping preferably has the relation of similar figures withthe outer circumferential geometry of the final-stage rolling roller 9used for final shaping as shown in FIG. 5. In a test actually carriedout by using a first rolling roller 6 having a relatively acuminateshaping surface, the mark of the first rolling roller 6 was retained inthe groove of the pipe 2 even after the final shaping by the final-stagerolling roller 9. Therefore, it is desirable that shaping surfaces ofthe first to final rolling rollers have the relation of similar figures.

The foregoing explanation has been made as using four rolling rollers6˜9 to form the first locking groove 3 or the second locking groove 4 inthe pipe 2 by sequentially bringing them into tight rolling contact withthe pipe 2 transversally of the pipe 2. However, the number of stages ofthe rolling rollers is not limitative, and more stages (but not lessthan two) may be used for preliminary shaping and final shapingaltogether.

The foregoing explanation has been made as using a plurality of rollingrollers 6˜9 getting greater in diameter from the one first entering intothe guide hole 13 to the one finally entering into the guide hole 13,and aligning their rotation centers on a common vertical line L. In thiscase, the rolling rollers may be equal in thickness as well, or may bedifferent in thickness.

Alternatively, the rolling rollers may be equal in diameter. In thiscase, as shown in FIG. 6, the individual rolling rollers should besupported to lay their rotation centers gradually offset from that ofthe rolling roller 6 first compressing the workpiece 2 to the rollingroller finally compressing the pipe 2 by ΔL each in a direction normalto the direction of relative movement between the rolling rollers 6˜9and the pipe 2. Thereby, the biting depth B (FIG. 5) of the rollingrollers into the pipe 2, corresponding to the amount of depression ofthe pipe 2, can be increased gradually from that of the firstcompressing rolling roller 6 to that of the finally compressing rollingroller 9. In this modification using rolling rollers equal in diameter,shaping surfaces of the rolling rollers may be either identical orsimilar (different in thickness) as explained with reference to FIG. 5.

FIG. 6 shows a roller support block 10 supporting three rolling roller6˜8. In this example, the first and second rolling rollers are used forpreliminary shaping, and the uppermost third rolling roller 8 is usedfor final shaping.

FIGS. 7 and 8 show a test system 30 actually prepared as arecess-forming system according to an embodiment of the invention toconfirm expected effects of the present invention. Hereunder,explanation is omitted about some of the components of the test system30, which are identical to components already explained in conjunctionwith FIG. 1, by simply identifying them with common reference numerals.

FIG. 7 shows a pipe holder 5 of the test system 30. The pipe holder 5has a pipe-receiving horizontal hole 31 horizontally penetrating theholder main body 12 and having a round cross section. Diameter of thepipe-receiving horizontal hole (hereafter simply called pipe hole) 31 isapproximately equal to the diameter of the pipe 2 as a workpiece suchthat, when the pipe 2 is inserted into the pipe hole 31, there issubstantially no clearance between the pipe 2 and the pipe hole 31. Thepipe holder 5 further includes a sub block attached to one side surfaceof the holder main body 12 and having a horizontal groove continuousfrom the pipe hole 31; and a fixing block 11 having a horizontal groove33 and removably attached to the sub block. When the fixing block isattached to the sub block, their horizontal grooves can make a pipe holecontinuous from the pipe hole 31 in the holder main block 12. Therefore,after the pipe 2 is inserted in and through the pipe hole 31 of theholder main body 12 to partly lie on the horizontal groove of the subblock, once the fixing block 11 is tightly attached to the sub block bybolts 34, the pipe 2 is enveloped over its entire circumference by thepipe holder 5 and prohibited in lengthwise displacement and rotationabout its axis.

It is sufficient for the pipe holder 5 to envelope the entirecircumference of the pipe 2 only in its segment nearest to the portionwhere the recess should be formed. The other segments of the pipe 2 neednot be enveloped by the pipe holder over its entire circumference.Therefore, the terms, “envelope the pipe 2” used herein should beconstrued to envelope a part of the pipe 2, in which a recess should beformed. The pipe holder 5 enveloping the pipe 2 has a rectangular guidehole 13 vertically penetrating the pipe holder 5 at a location adjacentto the pipe hole 31.

FIG. 8 shows a roller support block 10 that is another component of thetest system 30. The roller support block 10 includes a main body 40having a rectangular cross-section and supporting two rolling roller 6,7 to permit free rotation in a vertically spaced relationship.

The two rolling roller 6, 7 are rotatably attached to the support blockmain body 40 via support shafts 15, 16 intersecting with a verticalaxial line L in alignment with the axial line of the support block mainbody 40. Diameter D1 of the first rolling roller 6 located lower isslightly smaller than the diameter D2 of the second rolling roller 7located upper as the final stage.

The roller support block 10 is inserted into the guide hole 13 of thepipe holder 5 from above to position the first rolling roller 6 lower.The guide hole 13 defines a pair of opposed vertical grooves 37 (seeFIG. 7) having a cross-sectional geometry corresponding to the shapingsurfaces of the first and second rolling rollers 6, 7 that projectoutwardly from side surfaces of the main body 40 of the roller supportblock 10 (see FIG. 8). It will be readily understood from theconfiguration of the vertical grooves 37 in the guide hole 13 that therolling rollers 6, 7 have shaping surfaces (outer circumferentialsurfaces) suitable for forming the locking groove 4 shown in FIG. 3.

One (37 a) of the opposed vertical grooves 37 in the guide hole 13,which is adjacent to the pipe-receiving horizontal hole 31, partlyinterferes with the pipe-receiving horizontal hole 31 and communicateswith it through an aperture 35 (see FIG. 9). The shaping surfaces of thefirst and second rolling rollers 6, 7 can compress the pipe 2 throughthe aperture 35.

FIG. 10 shows a part of the pipe 2 already having the locking groove 4,and shows where the aperture 35 is positioned relative to the groove 4when the groove is formed. The hatching in FIG. 10 shows the position ofthe aperture 35. The aperture 35 has a contour in form of the peripheraledge of the locking groove 4. However, a gap C may be provided between aperpendicular wall surface 36 (see FIG. 7) of the vertical groove 37 inthe guide hole 13 and the perpendicular side surfaces 6 a, 7 a (see FIG.9) of the first-stage and second-stage rolling rollers 6, 7 for formingthe engagement surface 4 a of the looking groove 4 a. The perpendicularwall surface 36, perpendicular side surfaces 6 a, 7 a and engagementsurface 4 a are planes perpendicular to the lengthwise direction of thepipe 2 held in the pipe-receiving hole 31. In this test system 30, thegap C equals 0.1˜0.2 mm approximately. However, in case of forming alocking groove configured as shown in FIG. 2 or 3, it is desirable toreduce the gap C to approximately zero in order to form the sharpengagement surface 4 a with a clearly angled edge. Therefore, to formthe sharp engagement surface 4 a with a sharply angled edge, it isdesirable that the aperture 35 has substantially no gap (C issubstantially zero) relative to the final-stage rolling roller 7. Thewording, “sharp engagement surface with (or having) a clearly anglededge”, means that the engagement surface of the recess extends straightinward of a workpiece in the direction crossing the lengthwise axis ofthe workpiece at a right angle, and makes a clearly angled edge at itsterminal end nearer to the outer circumferential surface of theworkpiece. The wording, “sharply angled edge”, means that the borderbetween the engagement surface 4 a and the outer circumferential surfaceof the pipe 2 or an intervening surface makes a clear angle not blunt orrounded. In case the engagement surface of the recess is formed toextend straight inward of the workpiece directly from the outercircumferential surface of the workpiece like those of the recesses 3and 4 shown in FIGS. 2 and 3, the “sharply angled edge” is the borderbetween the engagement surface and the outer circumferential surface ofthe workpiece. In this case, the angle of the sharply angled edge isapproximately a right angle. In another form of recess (not shown)having an inner wall surface first sloping down inward of from the outercircumferential surface of the workpiece and then turns to the directionperpendicularly to the lengthwise axis of the pipe, the edge of theengagement surface pertains to the border between the engagement surfaceand the sloping surface, and the angle of the edge will become largerthan 90°.

In use of the test system 30, the pipe 2 is set in the pipe holder 5 andfixed from lengthwise displacement and rotation about the axis. Then,the roller support block 10 in the guide hole 13 is moved first down andnext up to make one reciprocal motion. Thus, the locking groove 4 isformed in the pipe 4. In the process of forming the locking groove 4,since the pipe holder 5 envelopes the entire circumference of the pipe2, the test system 30 can prevent undesirable deformation of the pipe 2caused by compression onto the pipe by form rolling.

The pipe 2 used in the test was a high tension material, having atensile strength not lower than 650 N/mm², sized 12.7 mm in diameter andhaving the wall 1.4 mm thick. As a result, the locking groove 4 obtainedhas been confirmed to be in a practically satisfactory level withoutbluntness at the corner of the engagement surface 4 a.

The problem of bluntness or dullness of the edge of the engagementsurface was examined. As a result, although the above-mentioned gap Caround 0.1˜0.2 mm is acceptable, it has been confirmed more effective tominimize the gap C relative to the final-stage rolling roller 7 in orderto make an angled edge at the outer end of the engagement surface 4 a.In the test system 30 intended to form grooves shown in FIG. 2 or 3, thecontour of the aperture 35 is substantially the same as the contour ofthe final-stage rolling roller 7.

When the invention is used to form locking grooves of a headrest stay,two stages through five stages will be sufficient as the multiple stagesof rolling rollers for systems of a mass-production model. Additionally,it has been confirmed that minimization of diameters D of the rollingrollers is effective to prevent bluntness because the contact surface ofthe rolling rollers with the pipe 2 can be reduced. For example, pipes 2for headrest stays generally have a diameter around 10˜13 mm. For suchpipes 2, it is desirable to limit the diameter of the final-stagerolling roller to the diameter of the pipe 2 or to the level of 1˜4times the diameter of the pipe 2, or preferably in the range of 1˜3times the diameter of the pipe 2. The pipes 2 used in the test were 12mm and 12.7 mm in diameter, and the diameter of the final-stage rollingroller was 45 mm.

Heretofore, the test system 30 has been explained. When a recess-formingsystem of a mass-production model is designed under the same concept, itis recommended to prepare and simultaneously activate some rollersupport blocks 10 equal to the number of locking grooves 3, 4 to beformed in each pipe 2 to form the desired number of locking grooves 3, 4at the same time. If each pipe 2 needs some locking grooves 3, 4 inclose positions, it is more desirable to modify the roller support block10 to rotatable support corresponding sets of first to final rollingrollers side by side. That is, as shown in FIGS. 11 and 12, the commonroller support block 10 have four support axes 15˜18. The first supportaxis 15 rotatably supports six first rolling rollers 6(1)˜6(6) side byside as FIG. 11 shows. The second support axis 16 rotatably supports sixsecond rolling rollers 7(1)˜7(6) side by side. Similarly, the thirdsupport axis 17 and fourth support axis 18 rotatably support six thirdrolling rollers 8(1)˜8(6) and six fourth rolling rollers 9(1)˜9(6) sideby side, respectively. In this common roller support block 10, the firstrolling roller 6(1), second rolling roller 7(1), third rolling roller8(1) and fourth (final) rolling roller 9(1) constitute one set ofrolling rollers for forming one locking groove 3 or 4. Similarly, thefirst to fourth rolling rollers 6(2), 7(2), 8(2) and 9(2) constituteanother set of rolling rollers for forming another locking groove 3 or4. Thus, the common roller support block 10 shown here supports six setsof rolling rollers, and can be used to form six locking grooves 3, 4 atclose positions on one pipe 2 simultaneously. Note that FIG. 12 merelyshows the support axes 15˜18 and omits illustration of rolling rollerson these axes.

In a recess-forming system of a mass-production model, the fixing block11 may be designed to use hydraulic pressure to fix the pipe 2.

FIG. 13 shows a recess-forming system 100 embodying the invention.Hereunder, explanation is omitted about some of the components of therecess-forming system 100, which are identical to components alreadyexplained in conjunction with FIG. 1, by simply identifying them withcommon reference numerals. The recess-forming system 100 is a remodeledmachine from a mass-production model press. The roller support block 10of the recess-forming system 100 is fixed at the lower end of a shaft101 of a hydraulic cylinder (not shown), and movable up and down.

Below the roller support block 10, a guide member 102 having a guidehole 13 is placed stationary, and a pipe holder 105 is located adjacentto the guide member 102. The pipe holder 105 is composed of a lowerholder 106 and an upper holder 107. The upper holder 107 can be moved upand down by the hydraulic cylinder 108.

FIG. 15 is a view of the guide member 102 and the pipe holder 105 takenfrom a diagonally upper point. As shown in FIG. 15, the guide hole 13that receives the roller support block 10 is defined by the guide member102 and the pipe holder 105. On one side surface 105 a of the pipeholder 105 defining the guide hole 13, five vertical grooves 109 a˜109 eare formed to permit rolling rollers to travel. Each of the verticalgrooves 109 a˜109 e has a width substantially equal to the thickness ofthe outer circumferential portion of the final-stage rolling roller 9.In other words, the roller support block 10 supports five sets ofrolling rollers side by side, each set being composed of four rollingrollers 6˜9 arranged in four vertical stages. Thus, the roller supportbock 10 can form five locking grooves simultaneously in its singlereciprocal movement in the vertical direction.

As shown in FIG. 14, the stationary lower holder 106 and the movableupper holder 107 have horizontal grooves 106 a, 107 a having asemicircular cross section, respectively. The semicircular grooves 106a, 107 a are opposed to each other and, in combination, make ahorizontal cylindrical hole receiving the pipe 2. The horizontalcylindrical hole made by the semicircular grooves 106 a and 107 a issized substantially equal to the outer contour of the pipe 2 at leastover a partial length thereof for receiving the groove-forming portionof the pipe 2. The other part of the horizontal cylindrical hole made bythe semicircular grooves 106 a and 107 a may be sized larger than thediameter of the pipe 2.

Still referring to FIG. 14, the upper holder 107 is urged downward bythe hydraulic cylinder 108, and can firmly grip the pipe 2 to preventundesirable rotation and displacement in the lengthwise direction. Whilethe pipe 2 is gripped firmly in this manner, when the roller supportblock 10 moves vertically in the guide hole 13 by one reciprocation,sets of the first to final rolling rollers 6˜9 form a correspondingnumber of locking grooves 3,4 simultaneously. When the piston 108 a ofthe hydraulic cylinder 108 withdraws, the upper holder 107 lifts up andloosens the grip to the pipe 2 to permit it to be removed from the pipeholder 105.

In a certain environment, it may be convenient to divide the pipe holder105 to right and left holder halves and fix one of these holder halvesadjacent to the guide member 102 stationary while permitting the otherto move. In this design, when four-stage rolling rollers 6˜9 applypressure to the pipe 2 during vertical reciprocation of the rollersupport block 10, the pressure from the rolling rollers 6˜9 mayundesirably displace the movable holder half to the right or left thoughslightly. In this case, the pipe 2 may undesirably deform due to thestress produced by the forming of recesses.

However, in the state where the upper holder 107 overlies the lowerholders 106, the semicircular horizontal grooves 106 a, 107 a make thehorizontal cylindrical hole substantially equal in diameter to the pipe2, and prevents deformation of the pipe 2 when recesses are formed bythe rolling rollers 6˜9.

Heretofore, application of the invention to locking grooves of aheadrest stay has been explained. However, the invention is of courseapplicable to formation of recesses for check balls of hollow shift forkshafts. Furthermore, the invention is widely usable for forming recessesin pipes in general.

Although some embodiments have been explained, it should be understoodby those skilled in the art that various modifications, combinations,sub-combinations and alterations may occur depending on designrequirements and other factors and that the present inventioncontemplates these modifications, combinations, sub-combinations andalterations insofar as they are within the scope of the appended claimsor the equivalents thereof. For example, the invention contemplates thefollowing modifications among others.

(1) The embodiments have been explained as moving the rolling rollers6˜9 relative to the pipe 2 to form the locking grooves 3, 4. However,the system may be designed to move the pipe 2 relative to the rollingrollers 6˜9. That is, it is sufficient that the rolling rollers 6˜9sequentially interfere with the pipe 2. Therefore, as shown in FIG. 13,a plurality of pipes 2 may be set movable to move transversally ofrolling rollers 6˜9 that are rotatable at fixed positions. In this case,the process of forming recesses 3, 4 may be completed either in one-waymovement of the pipes 2 transversally of the rolling rollers 6˜9, forexample, from left to right, or in one reciprocal movement of the pipes2.

(2) As a method of supporting the pipe 2, the above-explained embodimentuses the pipe hole 31 (best shown in FIGS. 7 and 9) having a circularcross section. To reliably prevent withdrawal of the pipe 2 while therecesses 3, 4 are formed, it is effective to provide a wall withholdingthe surface of the pipe 2 opposite from the recess-forming portion(shown by triangles in FIG. 10).

(3) In the foregoing embodiments, the rolling rollers 6˜9 arefree-rotation rollers. However, they may be power-driven rollers thatcan rotate with power from a drive means.

(4) In the foregoing embodiments, a single set of rolling rollers inmultiple stages includes a single final-stage rolling roller. However,each set of multi-stage rolling rollers may include two or morefinal-stage rolling rollers. In this case, two or more final-stagerolling rollers are adjacent to each other, and they are identical inshape and size. In the embodiments aligning the center axes of therolling rollers on a common straight line L (see FIGS. 1 and 14), two ormore final-stage rolling rollers are of course aligned to lay theircenter axes on the common straight line L. In the embodiment usingrolling rollers equal in diameter, although the rolling roller indifferent stages are sequentially offset by Δ (see FIG. 6), two or morefinal-stage rolling rollers should be supported to lay their center axeson a common straight line.

1. A method of forming a recess in a tubular workpiece comprising:preparing a set of rolling rollers in multiple stages capable ofsequentially interfering the workpiece in an intersecting direction;having the rolling rollers sequentially get into pressure contact withthe workpiece by relative movement between the rolling rollers and theworkpiece to bring about preliminary shaping and final shaping andthereby form the recess in the workpiece; and preparing a workpieceholder capable of holding the workpiece immovable by enveloping theworkpiece and having an aperture through which the rolling rollers cansequentially interfere with the workpiece, wherein the rolling rollersget into pressure contact with the workpiece through the aperture. 2.The method according to claim 1 wherein the final-stage rolling rolleramong the set of rolling rollers, which finally comes into pressurecontact with the workpiece, makes substantially no gap between sideedges thereof and opposed edges of the aperture, and thereby forms therecess with a sharp engagement surface.
 3. The method according to claim2 wherein the contour of the recess is substantially equal to thecontour of the aperture.
 4. The method according to claim 1 wherein themulti-step rolling rollers are freely rotatable.
 5. The method accordingto claim 4 wherein diameters of the multistage rolling roller aresmaller the four times the diameter of the workpiece.
 6. The methodaccording to claim 1 further comprising: preparing plural sets of therolling rollers in multiple stages, and using them simultaneously to aplurality of said recesses simultaneously.
 7. A method of forming arecess in a tubular workpiece, comprising: preparing a workpiece holderhaving an aperture through which the rolling rollers can sequentiallyinterfere with the workpiece and capable of holding the workpieceimmovably by enveloping the circumference thereof, and a set of rollingrollers in multiple stages capable of getting in pressure contact withthe workpiece through the aperture; and having the rolling rollerssequentially get into pressure contact with the workpiece through theaperture to bring about preliminary shaping and final shaping andthereby form the recess in the workpiece.
 8. The method according toclaim 7 wherein all of the rolling rollers in multiple stages areidentical in diameter, and center axes of the rolling rollers indifferent stages are sequentially offset in the direction perpendicularto the lengthwise axis of the workpiece held in the workpiece holder. 9.The method according to claim 7 wherein the rolling rollers in differentstages vary in diameter sequentially in one direction, and center axesof all rolling rollers in multiple stages lie on a straight lineparallel to the lengthwise axis of the workpiece held in the workpieceholder.
 10. A system for forming a recess in a tubular workpiececomprising: a roller support block that holds a set of rolling rollersin multiple stages aligned in a row and permits the individual rollingrollers to rotate; and a workpiece holder having a workpiece-receivinghole substantially equal in cross-sectional configuration to theworkpiece and capable of holding the workpiece immovably in theworkpiece-receiving hole, said workpiece holder having an apertureexposing a part of the workpiece held in the workpiece-receiving hole,wherein the rolling rollers sequentially come into pressure contact withthe workpiece through the aperture along with relative movement betweenthe roller-receiving block and the workpiece holder, and therebyperforming preliminary shaping and final shaping sequentially to formthe recess in the workpiece.
 11. The system according to claim 10wherein plural sets of rolling rollers in multiple stages are provided.12. The system according to claim 10 wherein one of the rolling rollersin the final stage in each set makes substantially no gap between a sideedge of the outer circumferential portion thereof and the contour of theaperture, and can make a sharp engagement surface having an angled edgein the recess in the workpiece in alignment with the contour of theaperture.
 13. A system for forming a recess in a tubular workpiececomprising: a roller support block that holds a set of rolling rollersin multiple stages vertically aligned in a row and permits theindividual rolling rollers to rotate; a guide member having a guide holefor guiding vertical movements of the roller support block; a hydrauliccylinder vertically driving the roller support block under the guide bythe guide hole; and a workpiece holder located horizontally adjacent tothe guide member and having a workpiece-receiving hole having a contoursubstantially identical to the cross-sectional configuration of theworkpiece at least in a portion thereof for supporting a portion of theworkpiece to be processed to form a recess therein, said workpieceholder being capable of holding the workpiece immovably in theworkpiece-receiving hole, wherein said workpiece holder having anaperture through which the rolling rollers can sequentially interferewith the workpiece held immovably in the workpiece-receiving hole topermit the rolling rollers in multiple stages to come into pressurecontact with the workpiece and thereby perform preliminary shaping andfinal shaping sequentially to form the recess in the workpiece.
 14. Thesystem according to claim 13 wherein the roller support block supportshorizontally aligned plural sets of the rolling rollers in multiplevertical stages.
 15. The system according to claim 13 wherein theaperture has a contour substantially equal to the contour of the recessformed in the workpiece.
 16. The system according to claim 13 whereinone of the rolling rollers in the final stage makes substantially no gapbetween a side edge of the outer circumferential portion thereof and aside edge of the aperture, and can make a sharp engagement surfacehaving an angled edge in the recess in the workpiece in alignment withsaid side edge of the aperture.
 17. The system according to claim 13wherein the workpiece holder is composed of a lower holder half and aupper holder half both having elongated grooves in form of upper andlower halves of said workpiece-receiving hole, said upper holder halfbeing driven vertically by a second hydraulic cylinder.
 18. The systemaccording to claim 12 wherein the rolling rollers in multiple stageshave the relation of similar figures.
 19. A method of forming a recessin a tubular workpiece held immovably, comprising: preparing a set ofrolling rollers identical in diameter and aligned in a row perpendicularto the lengthwise direction of the workpiece; and having the rollingrollers sequentially roll on and compress the workpiece along withrelative movement between the rolling rollers and the workpiece to forma recess at the compressed portion of the workpiece, said recess havinga plane perpendicular to the lengthwise direction of the workpiece,wherein center axes of said rolling roller equal in diameter aregradually offset from an imaginary line parallel to said relativemovement so that the amount of depression of the pipe made by sequentialcompression by the rolling rollers increases gradually.
 20. The methodaccording to claim 2 wherein the multi-step rolling rollers are freelyrotatable.